The process of the invention concerns the preparation of iodoalcohols having a perfluoroalkyl chain.
This process consists of adding a perfluoroalkane iodide CF.sub.3 (CF.sub.2).sub.n I, which is designated herein by the generic term "R.sub.F I", onto an ethylenic alcohol.
Various processes are known which permit the reaction of R.sub.F I iodides with ethylenic compounds. However, these processes give only mediocre yields in the case of ethylenic alcohols and especially in the case of allyl alcohol.
This reaction can, for instance, be carried out by the use of radicals initiating the reaction by an elevation of temperature (R. N. Haszeldine, J. Chem. Soc. 1953, p. 1199; U.S. Pat. Nos. 3,016,406 and 3,016,407), by irradiation with ultraviolet rays (R. N. Haszeldine's article cited above; J. D. Park, J. Org. Chem. 26, 1961, p. 2086, and C. Cantacuzene, J. Chem. Soc. Perkin I, 1977, p. 1365), or by the use of azoic derivatives (N. O. Brace, J. Org. Chem. 27, 1962, p. 3027 and U.S. Pats. Nos. 3,083,224, 3,145, 222, and 3,257,407).
It is likewise possible to catalyze the addition by Assher's system (J. Chem. Soc. 1961, p. 2261), with the catalyst being a mixture of cuprous and cupric salts and of amines. This process was extended to fluorinated molecules by D. J. Burton (Tetrahedron Letters 1966, p. 5163), N. O. Brace (J. Org. Chem. 44, 1979, p. 212) and described in French Pat. No. 2,103,459.
Although all of these systems make it possible to reach R.sub.F I with an ethylenic compound, they present the drawback of resulting only in mediocre (low) and very variable yields, depending on the nature of the initiator and the nature of the olefin used. A universal catalyst does not exist and, in particular, there is no system capable of causing the quantitative addition of R.sub.F I onto ethylenic alcohols. Thus, the photochemical addition according to J. D. Park , or the process described in French Pat. No. 2,103,459, yield a degree of conversion of only 50-55% with allyl alcohol.